Lyme disease is the most prevalent arthropod borne infection in the United States, and has shown a steady increase in incidence since its discovery. The spirochete Borrelia burgdorferi is the causative agent. Very little is known about the B. burgdorferi virulence attributes that bring disease to the host. The present proposal focuses on the chemotaxis and motility of B. burgdorferi, and their rote in the disease process. Chemotaxis and motility are likely to be important virulence attributes, as these organisms penetrate into tissues and organs where other bacteria fall to invade. Basic to an understanding of chemotaxis on a molecular level, in Aim 1 we will identify those compounds that serve as attractants. Putative chemoattractants will be identified from information drawn from the genome sequence and known metabolism of B. burgdorferi The chemotactic ability of these compounds will be tested using established methodology. Both high passage (avirulent) and tow passage (virulent) strains will be tested under appropriate environmental conditions. in Aim 2, we propose to construct both insertion-deletion and in-frame deletions mutations in specific motility and chemotaxis genes. Both high and low passage strains will serve as parental strains. We hypothesize that each of these mutants will have a distinct phenotype. These phenotypes will be analyzed with respect to motility, chemotaxis, structure, western blot, proteomics and transcriptional analysis using DNA-microarray technology. To insure that a given phenotype is due to the targeted mutation being studied, we will use gene-complementation analysis. in Aim 3, we will test the hypothesis that motility and chemotaxis are important virulence attributes of B. burgdorferi. To test this hypothesis, we will use standard cell penetration assays, and the mouse model of Lyme disease. We predict that the motility and chemotaxis mutants will be less invasive and virulent than the parental strains in both of these assays. The experiments proposed should yield information with respect to the roles of chemotaxis and motility of B. burgdorferi in Lyme disease, and perhaps lay the foundation for new methods for prevention and treatment. [unreadable] [unreadable]